a complete metric system of units of measurement for scientists; fundamental quantities are length (meter) and mass (kilogram) and time (second) and electric current (ampere) and temperature (kelvin) and amount of matter (mole) and luminous intensity (candela)

the system of weights and measures based on the foot and pound and second and pint that dates back to colonial America but differs in some respects from the British Imperial System; today in the United States this system exists side by side with the SI system